The present invention relates to an apparatus for supplying hot water comprising a thermodynamic system having compressor means, a condenser constituting the high temperature source associated with heat exchange means for transferring heat to a hot-water circuit, an expansion valve and heat-exchange evaporator means for heat exchange with a liquid constituting a cold source.
Numerous installations of that type are known for producing hot water for industrial or domestic needs (supply of sanitary or heating water more especially).
When the heating needs are the highest, i.e. when the ambient temperature is lowest (typically in winter), the performance coefficient of the heat pump drops and may approach 1 when the cold source is at the temperatures usually available at that time. The "performance coefficient" is the ratio between the thermal energy supplied to the heat source by the apparatus and the overall electric energy supplied to the apparatus, particularly to the compressor thereof.
There is disclosed in French Pat. No. 2,439,954 an apparatus of the kind having a thermodynamic circuit through which flows a refrigerant or thermodynamic fluid in liquid and vapor phases; the circuit comprises a compressor unit, a condenser for heat-exchange with a high temperature source for transferring heat to a hot-water circuit, an expansion valve and an evaporator for heat-exchange with a circuit in which flows a heat-carrying liquid of a cold source including a sun energy collector for heating said heat-carrying liquid, thermal storage being ensured by the latent freezing heat of a body of water contained in a tank. Means for heat exchange between the heat carrying liquid and water comprise an exchanger immersed in the body of water. This arrangement leads to freezing of the water as a solid body during severe cold, which creates problems of deicing, of guaranteeing operation and of excessive time for returning to a high performance coefficient.
A solar radiation collector using the greenhouse effect for heating water which flows in exchangers has been described in German specification No. 2,649,872. But solar radiation has disadvantages: it is not available at night; in the daytime it is uncertain.
It is an object of this invention to provide an improved apparatus for supplying hot water; it is a more particular object to achieve a performance of merit coefficient substantially higher than 1 and to overcome the uncertainties of solar heating.
To this end, an apparatus of the above-defined kind has heat exchange means placed in the heat-carrying circuit above the storage tank, associated with a pump for taking water from said body and feeding it to distributor means for sprinkling said water on said exchange means. The apparatus consequently forms an ice works when the solar energy make-up becomes insufficient. Defrosting means are provided for melting the ice in contact with the exchange means with heat energy taken from the apparatus. That energy may be that delivered by the solar exchanger and stored; the apparatus may be designed so that heat make-up may be supplied exceptionally by the water of the water-distribution network.
In a particular embodiment, the heat exchange means and the evaporator form a same unit placed above the tank. This arrangement presents advantages as regards the performance coefficient which it is possible to obtain.
In a modified embodiment, the heat exchange means, disposed above the tank, are separate from the evaporator, in which heat exchange takes place between the thermodynamic fluid and the heat-carrying liquid. Then, to reduce the temperature difference between the water in the tank and the thermodynamic fluid to an acceptable value and to compensate for continuous operation of the pump of the solar exchanger, the heat exchanger is given an exchange area substantially greater than that required in the case of the preceding embodiment. On the other hand, the exchanger is of simpler construction and may be constructed by low-cost processes, with materials of moderate cost. An exchanger may further be used made from modules formed from laminated aluminium or light-alloy sheets provided with contact bosses and forming a flow circuit for the unfreezable fluid. Each of these modules may be obtained by the so-called "roll-bond" laminating and securing technique.
The invention will be better understood from the following description of particular embodiments thereof given by way of examples only.